Method And Apparatus For A Signal Selective RF Transceiver System

ABSTRACT

Method and apparatus to dynamically configure the signal reception selectivity of a plurality of transceivers is described. In one embodiment, a transceiver includes a receiver circuit having two or more filter circuits. Each of the filter circuits is configured to pass RF signals from a different portion of an overall receiver bandwidth. When two or more receivers in proximity to one another are simultaneously operating, the filter circuits of the respective receiver are dynamically configured to different RF frequency passbands to minimize interference and cross talk between receivers and transmitters.

COPYRIGHT NOTICE

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent file or records, but otherwise reserves all copyrightrights whatsoever.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/621,687, entitled “Method And Apparatus For A Signal Selective RFTransceiver System” filed Jul. 17, 2003.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to wirelessdevices and more specifically to receiving and transmitting signalsbetween transceivers.

2. Description of the Related Art

Generally, a communication system includes a transmitter and receiverwhich transmit and receive information signals over a transmission mediasuch as wires or atmosphere. When atmosphere is used, the transmissionis commonly referred to as “wireless communication”. Examples of varioustypes of wireless communication systems include digital cellular, packetdata paging, wireless local area networks (LAN), wireless wide areanetworks (WAN), personal communication systems, and others.

One problematic issue relates to increasing wireless network capacity.As more users are added to a wireless network, the more information eachwireless network transceiver (card) is required to handle. Others haveattempted to solve this issue by using a plurality of wireless networkcards to increase wireless system capacity. To minimize floor spaceusage, often the plurality of wireless network cards are placed in a“rack” system, often in close proximity to one another. This methodologyalso allows the sharing of electrical power and communication bussesbetween the various wireless network cards for common control thereof.Unfortunately, transmitters and receivers of the wireless network cardsplaced in proximity to one another can cause cross talk and interferenceissues. For example, consider the case of co-located devices where atransmitter A is positioned in proximity to a receiver B, andtransmitter A and receiver B are operating at approximately the sameradio frequency (RF). Due to the spatial proximity between transmitter Ato receiver B, when transmitter A is transmitting a RF signal to anotherreceiver C, the output power of transmitter A may overload the input ofreceiver B, especially if receiver B has increased its input sensitivityto receive a weak signal from a distant transmitter (D).

As just described, this problem is particularly serious when onewireless network card is transmitting while another is receiving. Somewireless networking systems employ protocols that can be configured toavoid this situation. For example, Time Division Multiple Access (TDMA)systems allow the base station to control when each device transmits orreceives. In this way, co-located devices could be scheduled such thatone does not transmit while the other is receiving. Code DivisionMultiple Access (CDMA)_systems have coding gain. By assigning differentcodes to the co-located devices, the damage that occurs when onetransmits while another is receiving can be minimized. Finally, somewireless communication systems are based on polling, which like TDMAallows the transmissions of each device to be controlled by acentralized controller which transmits the polis allowing individualdevices to transmit. By proper timing of the polling, the case of oneco-located device transmitting while another is receiving can beavoided.

Others have tried to correct the problem of uncoordinated transmissiontimes, where a co-located device transmits while another receives, byusing wireless network cards having narrow RF filters that limit eachcard to specific frequencies of operation. Unfortunately, thismethodology may require procuring and maintaining a stock of differentwireless network cards for each narrow frequency sub-range. Still othershave tried to use spatially separated antennas or used directionalantenna systems. Some have used time sharing solutions where only onewireless card is allowed to communicate at a time. All of the abovesolutions generally add complexity, reduce flexibility or performance,and increase the overall cost of the wireless network.

SUMMARY OF THE INVENTION

The present inventors have realized the need to configure a plurality ofadjacent wireless network circuits to operate simultaneously withoutreducing communication system efficiency and increasing cost andcomplexity. An aspect of the present invention is a radio frequency (RF)receiver including a RF filter circuit configured to dynamically selectan available frequency range from a plurality of frequency ranges, and aRF processing circuit configured to signal process a RF signal passedthrough the RF filter circuit.

An aspect of the present invention is a RF wireless network thatincludes at least two RF transceiver circuits. Each of the at least twoRF transceiver circuits being configured to select between a pluralityof frequency channels. The wireless network system also includes aprocessor configured to determine different available frequency channelsfrom the plurality of frequency channels for each of the at least two RFtransceiver circuits.

An aspect of the present invention is a method for selecting a RF signalreception frequency range. Available RF frequency ranges are determinedfrom a plurality of RF frequency ranges. One receiver is configured toreceive one of the available RF frequency ranges. Another receiver isconfigured to receive another of the available RF frequency ranges.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is a high-level schematic diagram illustrating one embodiment ofan exemplar wireless network system in accordance with one or moreaspects of the present invention;

FIG. 2 is a high-level schematic diagram illustrating one embodiment ofa receiver of the wireless network system of FIG. 1 in accordance withone or more aspects of the present invention;

FIG. 3 is a diagram showing possible arrangements of filter pass bandsand transition bands relative to frequency allocations;

FIG. 4A is a diagram of an antenna module according to an embodiment ofthe present invention that can be attached to one or more cards in asystem;

FIG. 4B is a diagram of an antenna module according to an embodiment ofthe present invention illustrating an example placement of the filters,switches, and antennas that can be attached to, for example, a genericwireless network card; and

FIG. 5 is flow diagram of one embodiment of a method for dynamicallyconfiguring a plurality of wireless network circuits in accordance withone or more aspects of the present invention.

It is to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the present invention may admit toother equally effective embodiments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the following description, numerous specific details are set forth toprovide a more thorough understanding of the present invention. However,upon review of the present disclosure, it will be apparent to one ofordinary skill in the art that the present invention may be practicedwithout one or more of these specific details. In other instances,well-known features have not been described in order to avoid obscuringthe present invention. Aspects of the present invention are described interms of wireless RF transmission and reception in an IEEE 802.11a andIEEE 802.11b regulated environment; however, other wireless transmissionand reception environments are contemplated.

FIG. 1 is a high-level schematic diagram illustrating one embodiment ofan exemplar wireless network system 100 in accordance with one or moreaspects of the present invention. In general, wireless network system100 may operate within a wireless local area network (LAN), a wirelesswide area network (WAN), and the like. In a particular embodiment, thewireless network is connected to larger networks such as the Internet.In one aspect, wireless network system 100 includes a plurality ofwireless network circuits 102A-N, where N represents an “Nth” number ofwireless network circuits 102A-N. Wireless network circuits 102A-Ninclude wireless network devices such as wireless adapters, wirelessnetwork interface cards (NIC), and the like. Wireless network circuits102A-N may communicate with one or more other wireless devices disposedinternal and external to the wireless network system 100. Wirelessnetwork circuits 102A-N will be described further with respect to FIG. 2and 3.

Wireless network system 100 includes one or more antennas 106A-N where Nrepresents an “Nth” number of antennas 106A-N. Each antenna 106A-N iscoupled to a respective wireless network circuit 102A-N. Antennas 106A-Nare configured to receive and transmit signals to and from the wirelessnetwork circuits 102A-N as known in the art. Other more advancedmultiple antenna techniques may also be utilized.

Wireless network system 100 also includes controller 108. Controller 108is configured to dynamically configure wireless network circuits 102 todifferent operational frequency channels relative one another via, forexample, control signals 112 and 114, respectively, described below.Controller 108 includes Central Processing Unit (CPU) 116 and a memory110. The CPU 116 may be under the control of an operating system thatmay be disposed in the memory 110. Illustrative operating systems, whichmay be used to advantage, include Linux and Microsoft's Windows®. Moregenerally, any operating system supporting the configuration functionsdisclosed herein may be used. The memory 110 is preferably a randomaccess memory sufficiently large to hold the necessary programming anddata structures of the invention. While the memory 110 is shown as asingle entity, it should be understood that the memory 110 may in factcomprise a plurality of modules, and that the memory 110 may exist atmultiple levels, from high speed registers and caches to lower speed butlarger direct random access memory (DRAM) chips.

Illustratively, the memory 110 may include a wireless deviceconfiguration program 114 that, when executed on CPU 116, configureswireless network circuits 102A-N to different frequency channels ofoperation. The wireless device configuration program 114 may use any oneof a number of different programming languages. For example, the programcode can be written in PLC code (e.g., ladder logic), a higher levellanguage such as C, C++, Java, or a number of other languages. While thewireless device configuration program 114 may be a standalone program,it is contemplated that wireless device configuration program 114 may becombined with other programs. For example, the wireless deviceconfiguration program 114 may be combined with other wireless deviceprograms configured to allocate channel usage between other wirelessnetworks.

In one embodiment, wireless device configuration program 114 configureswireless network circuits 102A-N to operate on different frequencychannels or frequency sub-channels relative one another. For purposes ofclarity, frequency channels and frequency sub-channels will be describedherein as frequency channels. Wireless device configuration program 114may configure wireless network circuits 102A-N to operate on differentfrequency channels relative to other external wireless systems inproximity thereto. A channel is defined herein as any frequency, orrange of frequencies, that are spaced separately in frequency. Forexample, consider the case of a RF signal having an operational range of2.4 GHz to 2.48 GHz. For a 10 MHz channel bandwidth, such RF signal mayhave, for example, up to 8 frequency channels depending on the frequencyspacing and guard-band between the frequency channels.

FIG. 2 is a high-level schematic diagram illustrating one embodiment ofa wireless network circuit 102A of the RF transceiver of FIG. 1 inaccordance with one or more aspects of the present invention. Forpurposes of clarity, wireless network circuit 102A will be described interms of receiving a signal from antenna 106A; however, in variousembodiments, wireless network circuit 102A is used to couple a RF signalto antenna 106A for transmission therefrom. In one embodiment, multipleantennas are connected to wireless network circuit 102A in parallel orthrough a switching device.

In general, wireless network circuit 102A includes switch circuit 120, aplurality of RF filter circuits 122A-N, switch circuit 124, andtransceiver 128. Switch circuit 120 includes an input electricallyconnected to antenna 106A. Switch circuit 120 includes multiple outputs,where one output is coupled to an input of a respective one of aplurality of RF filter circuits 122A-N, where N represents an “Nth”filter circuit 122A-N. Each RE filter circuit 122A-N includes an outputconnected to a respective input of switch 124. Switch 124 is configuredto connect an output of one of the RF filter circuits 122A-N to an inputof transceiver 128. Switch circuits 120 and 124 may be selected from aplurality of switches configured to pass RF signals such as PIN diodeswitches, GaAs FET switches, coaxial switches, and the like. Each RFfilter circuit 122A-N is configured to have a different frequencypassband relative to the other RF filter circuits 122A-N. In oneconfiguration, each RF filter circuit 122A-N is configured to have afrequency passband correlating to a respective frequency channel. Forexample, given a wireless network system 100 having ten frequencychannels and ten RF filter circuits 122A-N, each of the ten RF filtercircuits 122A-N may be configured with a frequency passband correlatingto one of the ten frequency channels. However, to reduce the cost andsize of the solution, it may be advantageous to use fewer filters. Forexample, only two filters might be used. In that case, each filter wouldhave a passband wide enough to allow 5 different frequency channels topass through the filter. Control signals 112 and 114 may be used to setswitch 120 and switch 124 so that one of a RF filter circuits 122A-N iscoupled to antenna 106A and to transceiver 128. In one aspect,controller 118 is configured to set control signals 112 and 114responsive to an analog signal wherein changes to such an analog signalcause the control signals to set switch positions of switch 120 andswitch 124. In another aspect, control signals 112 and 114 are coupledto and responsive to digital signals from controller 108 wherein changesto such digital signals result in changes of switch positions of switch120 and switch 124.

It is generally more difficult and expensive to build filters with veryabrupt transitions from a pass band to a stop band. Therefore, in thecase of a contiguous set of channels, it may be more efficient to allowoverlapping between the filter passbands. Consider options 3A, 3B, and3C illustrated in FIG. 3. In cases that the filter passbands overlap(e.g., options 3A and 3B), the frequencies within the overlap are usedonly if there is sufficient distance between the transceivers to preventoverloading without the benefit of filtering. In more favorablecircumstances, there may be a natural gap in the allocated frequenciesfor a particular application.

For example, the FCC currently allocates the band 5.15-5.35 GHz as wellas the band 5.725-5.825 GHz to wireless LANs. In this case, it isnatural to put one filter passband from 5.15-5.35 GHz, and anotherfilter passband from 5.725-5.825 GHz. In this case, the transitionregion of the filters occur between 5.35 and 5.725 GHz, in which neithertransceiver is allowed to operate due to government regulations. Thisallows all available channels in one of the bands to be used by a firsttransceiver without overloading a second transceiver operating in theother band, even if the two transceivers are located physically near toeach other.

Again, FIG. 3 shows these options. Option 3A illustrates a case wherefrequencies in a filter transition region are usable, due to eithersufficient filtering at the transition region and/or sufficient distancebetween transceivers. Option 3B illustrates the opposite case wherethere is either insufficient filtering and/or the transceivers are intoo close of a proximity to each other. Option 3B illustrates atransition region that occurs in an unallocated frequency range.

Control signal 112, 114 may be used to set switch 120 and switch 124 sothat one of a RF filter circuit 122A-N is coupled to antenna 106A and totransceiver 128. In one aspect, control signal 112, 114 may beconfigured responsive to an analog signal wherein changes to such ananalog signal result in changes of switch positions of switch 120 andswitch 124. In another aspect, control signal 112, 114 is coupled to andresponsive to digital signals from controller 108 wherein changes tosuch digital signals result in changes of switch positions of switch 120and switch 124.

In practice, it may be desirable to implement the RF filters in aseparate module that can be connected to a standard card that can coverthe full range of available frequencies. The standard cards are the typeof cards used at the mobile clients where more than one radio card arenot generally employed (e.g., PCMCIA, Cardbus, or mini-PCI cards). Theseparate module implementing the RF filters is configured with, forexample, a connector that fits a corresponding connector on the card.

In addition, inexpensive base stations or access points may alsoprimarily be constructed with a single radio that can tune over all theavailable channels. In this case, if the filters are constructed in aseparate module, the separate module may have a connector interface thatmates to a corresponding connector on the base station or access point.

FIG. 4A shows a way in which standard cards can be coupled to a separatemodule. In one embodiment, the module includes just the additionalsub-band RF filters. In another embodiment, the module includes thefilters and antennas. When antennas are included in the module, theantennas may be mounted, for example, at some distance, or in specificorientations such that the coupling between antennas is reduced (e.g.,at opposite ends of the module) . This will in turn reduce therequirements on the filters in order to prevent overloading of thereceive filters.

In the case that the number of frequency sub-bands is equal to thenumber of radio cards, a single filter module can be attached to eachradio card. This is sufficient for the cases in which the only stronginterference concerns come from the radio cards present within thesingle Access Point (AP). This is shown in FIG. 4 a. In the case thatmore frequency sub-bands are desired, multiple filters, together withswitches to select the appropriate filter are included in the module. Amodule containing enough sets of filters and switches for each wirelesscard is then attached to the wireless cards. Alternatively, a singlecard with a set of the described filters and switches is attached toeach radio card. These arrangements are beneficial if strong signalsthat could cause receiver overloading are expected from sources that arenot within the AP itself.

Such assemblies (e.g., single filter modules or modules with multiplefilters and selection switches) can be sold as an aftermarket additionor kit. In that case, the base station could be sold with a single radiocard originally. In the case that more communications capacity isdesired, a second radio card can be obtained, along with thefilter/antenna assembly. By inserting the second radio card into anempty slot in the base station and attaching the filter/antennaassembly, two radio channels can operate simultaneously withoutoverloading the receivers, thereby doubling the capacity of the basestation.

FIG. 5 is flow diagram of one embodiment of a method 300 for dynamicallyconfiguring a plurality of wireless network circuits 102A-N inaccordance with one or more aspects of the present invention. Method 300starts at 302 when, for example, wireless device configuration program114 is activated. At 304, frequency channel availability is determined.In one aspect, the frequency channel availability is determined bychecking the frequency channel of operation of one or more otherwireless network circuits 102A-N of wireless network system 100. Forexample, if one of the wireless network circuits 102A-N were configuredfor channel one, method 300 may configure another of the wirelessnetwork circuits 102A-N to channel two, and so forth. In another aspectof the invention, method 300 may utilize a lookup table stored in memory110 that establishes the frequency range of operation for each wirelessnetwork circuits 102A-N. For example, the table may specify that one ofthe wireless network circuit 102A-N be configured to channel one, whileanother of the wireless network circuits 102A-N is configured to channeltwo, and so forth. While the frequency of other wireless networkcircuits within the base station is of paramount concern, the use ofchannels by other base stations in the environment is a consideration aswell. Ideally, channels are chosen that do not conflict with thechannels being used by other base stations in the environment, as wellas ensuring that signals from each of the wireless network circuits donot overload other receivers in the base station.

The availability of a channel may be determined in a number of ways. Inone method, the receiver is activated, and the signal strength andfrequency of signal reception for one or more channels is evaluated.Channels that have strong or frequent signals present are considered tobe occupied and not available. In another method, sample transmissionscan be sent while monitoring the effect on other receivers within thebase station. If the transmissions can be sensed at the other receivers,or if the transmissions disrupt the communications of the otherreceivers, that channel is considered occupied and not available.Finally, if the transmitter being activated has an intended receiver ata remote location, the reliability and quality of the communicationslink can be sensed. If communication is poor or sporadic, it may bepossible to conclude that the frequency channel chosen is occupied andshould not be considered available.

In another aspect of the invention, method 300 may utilize a look-uptable stored in memory 110 that establishes the frequency range ofoperation for each wireless network circuit 102A-N. For example, thetable may specify that one of the wireless network circuit 102A-N beconfigured to channel one, while another of the wireless networkcircuits 102A-N is configured to channel two, and so forth.

At 306, if all of the frequency channels are available method 300proceeds to 308. At 308, method 300 configures each of the wirelessnetwork circuits 102A-N to a separate frequency channel and proceeds to316 end described below. In one aspect, one RF filter circuit 122A-N foreach wireless network circuit 102A-N is selected corresponding to arespective frequency channel allocation. The frequency channelallocation may be random or specified. For example, to balance frequencychannel usage and minimize interference, method 300 may configure eachof the wireless network circuits 102A-N so that the frequency channelsof operation are spread about evenly across the available frequencychannels. For example, method 300 may configure for ten frequencychannels and five wireless network circuits 102A-N, the five wirelessnetwork circuits 102A-N being configured to use all odd frequencychannels (i.e., frequency channels one, three, five, seven, nine) . Tominimize interference and cross talk, method 300 may increase thechannel spacing between adjacent receiving and transmitting wirelessnetwork circuits 102A-N. For example, if a very strong RF signal isbeing transmitted on channel one from a transmitting wireless networkcircuit 102A-N adjacent a wireless network circuit 102A-N that is tryingto receive a very weak signal, method 300 may increase the channelseparation between them. Illustratively, method 300 may configure thereceiving wireless network circuit 102A-N to a channel spaced furtheraway in frequency from the transmitting wireless network circuit 102A-N,such as channel ten. If at 306, not all frequency channels areavailable, method 300 proceeds to 310.

In another embodiment, method 300 may increase a physical distanceseparating transmitting and receiving wireless network circuit cards.For example, controller 108 is configured to assign which communicationchannels (e.g. frequencies) are utilized by the wireless network circuitcards 102A-102N. That is, a communication on a particular assignedchannel may be performed by any one of the cards 102A-102N as assignedby the controller. The controller assigns and/or dynamically re-assignscommunication channels handled by the network circuit cards based on aformula and/or criteria. For example, the controller (e.g., wirelessdevice configuration program 114) utilizes information such as a slotnumber in the system 100, information as to the location of the slot,the direction in which any directional antenna is transmitting, andstrength of incoming and transmitted signals. Then, channel assignmentsare, for example, made such that the network circuit card having thestrongest transmitted signal is physically as far away as possible fromthe network circuit card with the weakest received signal. Similarly,cards with antennas that are located close to each other can use widelyseparated channel frequencies, while cards with antennas that are farfrom each other may use smaller channel frequency spacing.

At 310, method 300 determines if at least one frequency channel isavailable. If at least one frequency channel is not available, thenmethod 300 returns to step 304. If however at least one frequencychannel is available, method 300 proceeds to 312. At 312, method 300determines which frequency channels to allocate for each of the wirelessnetwork circuits 102A-N. In one aspect, available frequency channels areallocated by examining the unused frequency channels and by determiningthe number of the wireless network circuits 102A-N being used. Asdescribed above, frequency channels may be allocated randomly or in aspecified order. For example, for a ten-channel system having threewireless network circuits 102A-N, the method 300 may allocate thefrequency channels for the three wireless network circuits 102A-Nrandomly. Method 300 may specify a specific order such as frequencychannels one, two, and three. Method 300 may also separate the frequencychannel usage by specifying frequency channels further apart such asfrequency channels one, five, and ten. Again, the allocation may alsotake into consideration existing and/or anticipated traffic onneighboring networks.

At 314, method 300 configures each wireless network circuit 102A-N for arespective channel allocation and ends at 316. In one aspect, a RFfilter circuit 122A-N having a passband corresponding to such arespective channel allocation is selected for each of the wirelessnetwork circuits 102A-N. For example, if a wireless network circuit102A-N is specified to operate on channel two, a RF filter circuit122A-N corresponding to the channel two wireless network circuit isconfigured to have a frequency passband for the frequency of channeltwo.

In one aspect, the wireless network circuits 102A-N may be dynamicallyreconfigured as needed. For example, if one wireless network circuit102A-N is not being used, its frequency channel of operation may be usedby another wireless network circuit 102A-N. When an unused wirelessnetwork circuit 102A-N is then needed, it may be reconfigured to anotheravailable frequency channel. Further, the wireless network circuits102A-N may be dynamically configured to adjust for dynamic frequencychannel usage. Illustratively, wireless network circuits 102A-N may bedynamically configured to different frequency channels when receivingsignals than when transmitting signals.

In yet another embodiment, if a wireless network circuit card beginstransmitting relatively high power signals and is physically close to awireless network circuit receiving weak signals, then the channels canbe reallocated to such that the high power transmitting and weak signalreceiving wireless network circuits are physically separated by as muchphysical distance as possible.

Referring back to the previous discussion regarding co-located devices,there are a number of wireless networks that use random accessprotocols. These protocols allow any device to begin transmitting at anytime. Many employ a listen before talk protocol to avoid collisionswithin the same channel. However, this mechanism does not preventco-located devices operating on different radio channels or frequenciesfrom beginning to transmit while another co-located device is receiving.Collision Sense Multiple Access (CSMA) and Distributed Control Function(DCF) are two common random access protocols. In particular, 802.11wireless networking devices utilize DCF, and are therefore random accessdevices. The techniques described herein are particularly valuable forsuch devices since there is not a mechanism within the DCF protocol tocoordinate the timing of transmissions from individual devices in thenetwork.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. An RF device comprising: a receiver configured to utilize a randomaccess communications protocol, each receiver being implemented on aradio card having a slot number and a slot location; a channel detectorconfigured to determine an available frequency from a plurality offrequencies; a filter circuit including a plurality of filters, eachfilter being associated with at least one frequency of the plurality offrequencies; and a controller configured to set the filter circuit topass the available frequency based on at least one of the slot numberand the slot location.
 2. The RF device according to claim 1, whereinthe device utilizes the 802.11 protocol.
 3. The RF device according toclaim 1, wherein the filter circuit includes at least one passbandfilter that passes the available frequency.
 4. The RF device accordingto claim 3, wherein the passband filter passes a band of 802.11regulated frequencies.
 5. The RF device according to claim 1, whereinthe filter circuit comprises a filter module detachably coupled to thereceiver.
 6. The RF device of claim 1, wherein each filter has adifferent passband.
 7. The RF device of claim 1, wherein each filterpasses a different frequency/passband.
 8. The RF device of claim 1,wherein the filter circuit is configurable to switch between sets of theplurality of filters.
 9. The RF device of claim 1, further comprising atransmitter, wherein the RF device is configured for simultaneoustransmission and reception.
 10. The RF device of claim 1, wherein therandom access protocol is one of CSMA and DCF.
 11. A method forselecting an RF signal reception frequency range, the method comprising:determining available RF frequency ranges from a plurality of RFfrequency ranges; selectively connecting a first receiver to a firstfilter to receive random access communications over a first available RFfrequency range; and selectively connecting a second receiver to asecond filter to receive random access communications over a secondavailable RF frequency range, the first and second filters being chosenfrom a plurality of filters, each filter of the plurality of filtersproviding a predetermined RF frequency range, each receiver beingimplemented on a radio card having a slot number and a slot location inan RF wireless network, each radio card being connectable to a set offilters, each set of filters being connectable to an antenna, whereinselectively connecting the first and second receivers is based on atleast one of the slot number and the slot location for each radio card.12. The method of claim 11, wherein determining includes detecting whichof the plurality of RF frequency ranges are occupied.
 13. The method ofclaim 12, wherein detecting includes determining if an RF signal isbeing transmitted or received within at least some of the plurality ofRF frequency ranges.
 14. The method of claim 11, further comprising:dynamically choosing each of the first and second filters from theplurality of filters, wherein each of the plurality of filters allows apredetermined frequency passband.
 15. The method of claim 11, whereineach filter allows a predetermined frequency passband.
 16. The methodaccording to claim 11, wherein the random access communications compriseat least one of CSMA and DCF.
 17. The method according to claim 11,further comprising: configuring at least one of the first and secondreceivers to receive Orthogonal Frequency Division Multiplexing (OFDM)signals.
 18. A method of operating a radio card in an RF systemincluding a plurality of radio cards, the method comprising: determiningat least one available frequency sub-band from a plurality of frequencysub-bands; configuring the radio card to use a selected availablefrequency sub-band; and configuring an add-on filter module to use theselected available frequency sub-band, wherein configuring the radiocard and the add-on filter module is based on at least one of a slotnumber and a slot location of the radio card.
 19. The method of claim18, wherein the plurality of radio cards is less than or equal to anumber of available frequency sub-bands.
 20. The method of claim 18,wherein the add-on filter comprises: a plurality of filters, each filterpassing one of the plurality of frequency sub-bands; and a switch toselectively connect one of the plurality of filters to the radio card.21. The method of claim 18, wherein the at least one available frequencysub-band includes at least one wireless network frequency.
 22. Themethod of claim 18, wherein the radio card is configured to utilize arandom access protocol.
 23. The method of claim 22, wherein the randomaccess protocol comprises one of CSMA and DCF.
 24. An add-on filterconnectable to at least one radio card, the add-on filter comprising: anRF filter mechanism configurable to a plurality of passbands; and atleast one RF connector for connecting the RF filter mechanism to the atleast one radio card.
 25. The add-on filter of claim 24, furthercomprising at least one antenna connector for connecting the RF filtermechanism to at least one antenna.
 26. The add-on filter of claim 25,wherein the RF filter mechanism includes a plurality of filters, eachfilter passing at least one passband.
 27. The add-on filter of claim 26,further comprising a first switch set for connecting each set of theplurality of filters to a radio card via an RF connector.
 28. The add-onfilter of claim 27, further comprising a second switch set forconnecting each set of the plurality of filters to an antenna via anantenna connector.
 29. The add-on filter of claim 26, wherein at leastone radio card uses a random access communications protocol.
 30. Theadd-on filter of claim 29, wherein the random access communicationsprotocol includes one of CSMA and DCF.